The present invention relates to an aqueous acid electroplating bath for producing extremely bright, lustrous electrodeposits of tin.
Various brightener compositions for acid tin baths containing carboxaldehydes are disclosed in several United States patents. Depending upon the particular aldehyde utilized, the electrodeposits from acid sulfate tin plating baths can vary from dull or semi-bright to bright. The choice of aldehydes also determines a plating bath's ability to produce bright plate in extremely high current density areas as well as at low current densities, such as those encountered in recesses of irregularly shaped parts.
It has been found according to the present invention that certain highly active alkoxy naphthalene carboxaldehydes as primary brighteners can be used in much lower concentrations than previously used aldehydes to produce electrodeposits of tin from an aqueous acid plating bath that exhibit extreme luster and brightness over a very broad current density range.